How much room does Bitcoin have upside in the future?
Still a lot of wiggle room to move, or at least wait for the last 3 halvings and we're pretty much reach almost all the bitcoin, (20 million supply). And from then on, we might see what will be the price, if it is going to be stable or not. Or if people are still going to trade it as commodity or treat it like money. So the future is still bright and the upside could be big in the future.
I definitely agree with your views. If someone had mentioned like 10 years ago that the price of Bitcoin was going to reach $60k+ and it was believed by everyone that even where in Bitcoin trading then, we definitely wouldn't have had the Bitcoin pizza moment. It was because they didn't see Bitcoin getting to this position that was why that happened.
Here we are now and I believe that there is still plenty of room for Bitcoin to further go up in price in the coming years because now we know better and until the total amount of Bitcoin has been mined price might continue upward.